In the field of motor-sweepers, it has long been known various structures that provide the possibility of regulating the position of the rotating brooms so that the distance between the surface being cleaned and their bristles is kept uniform despite their wear.
It is, in fact, known that the continuous friction with hard and rough surfaces involves the shortening of the bristles of the rotating brooms and consequently the pressure, with which the surface being cleaned is swept, is reduced.
In order to solve this drawback, the American U.S. Pat. No. 4,219,901 describes a motor-sweeper provided with an articulated device or apparatus that allows the operator to adjust the distance from the ground for a cylindrical broom mounted below and transversally with respect to the longitudinal axis of the same motor-sweeper.
The apparatus is provided with an articulated arm comprising a cylindrical body and a rod. An adjusting knob is on the base of the cylindrical body protruding from the motor-sweeper in the operator direction. On the opposite base, the one that stays inside the body of the motor-sweeper, a first threaded end of said rod engages, whereas on a second end there is fixed a C-shaped support adapted to support said cylindrical broom.
On the body of the rod there are fixed arms apt at modifying the attitude of the articulated arm between a resting position wherein the broom is lifted from the ground, and operating positions wherein the broom touches the ground with various pressures.
Instead, the adjusting knob allows to modify the overall length of the articulated arm.
The operator can manipulate said knob in order to apply a rotation to the cylindrical body of the articulated arm into a first direction, so that the first threaded end of the rod screws itself in the cylindrical body, or in the direction opposed to the first one, so that the first threaded end of the rod exits from the cylindrical body. Consequently, the distance from the ground of the axis of the cylindrical broom is increased, such as in the case of a new broom, or reduced as the bristles wear more and more, so as to always obtain the required pressure for a proper cleaning of the ground.
The motor-sweeper further comprises an exhaust blower that generates an air flow that helps in conveying the dust portion of the debris into a collecting container.
Also patent application US 2010/291843 describes a motor-sweeper provided with devices to adjust the distance from the ground of rotating brooms. In particular the described motor-sweeper is provided with two groups of brooms, one mounted at the front and one located centrally under the motor-sweeper. The second group comprises a cylindrical broom mounted transversally with respect to the longitudinal axis of the motor-sweeper and designated for collecting and conveying the dirt into a container located at the rear of the motor-sweeper. The distance from the ground of said cylindrical broom can be adjusted by the operator by means of a knob that makes the support of said broom swing about an axis so as to make it keep a proper contact with the surface being cleaned. It is to note that the pivot whereon the support axis of the broom swings, is located before the same broom, with respect to the forward direction of the motor-sweeper, so as to move the broom at the same time downward and forward. This movement makes it possible to keep constant the distance with a front flap for retaining and collecting the dirt collected by the broom. In fact, in order to ensure an efficient collection it is necessary not only that the broom is properly in contact with the ground but also that there is not too much space between the same broom and the front flap otherwise its rotation could not ensure the necessary push of the dirt at the rear toward the container.
Such devices only partially solve the problem of keeping constant the capability of collecting debris and garbage from the surface being cleaned due to the wear of the brooms.
In fact, with reference to the motor-sweeper described in the above-mentioned second prior art document, the conveying apparatus is certainly capable of adjusting the position of the transverse broom so that it remains in contact with the surface being cleaned and near the surface of the chamber wherein it is housed so as to convey debris and garbage upward, but in doing so it distances said rotating broom from the collecting container (FIG. 5A). Such progressive distancing of the rotating broom from the collecting container, necessary to balance the wear of the brooms and accordingly to fill the gap between the bristles or front flap, causes part of the garbage and debris to fall back down on the ground behind the broom forcing the operator to pass again on the areas already treated resulting in a waste of time, increase in the means wear, beside involving a lesser filling of the collecting container that therefore requires more stops to discharge the collected garbage and debris.
A similar motor-sweeper is also described in European patent application EP 0843046, wherein it is described a machine for cleaning the floor comprising a cylindrical rotating broom mounted on a rotation axis or hub whose ends are supported by an articulated intermediate frame in a position on the support frame of the same motor-sweeper (see column 4, lines 24-30). The position or the articulation axis enables the intermediate frame to adjust the position of the rotating broom with respect to the ground as a consequence of its wear (see column 4, lines 53-54 and column 6, lines 53-56). Moreover a leverage system allows a front flap to be adjusted so as to follow the broom adjustment downward at the front in order to keep there a continuous controlled distance.
Now, with reference to FIGS. 1, 2 and 4 it can be clearly seen that the articulation point which allows the above-said lowering movement of the intermediate frame to the ground, only involves the lowering of the broom toward the ground, therefore making up for the wear of the broom with respect to the ground and at the front, but not at the rear where the garbage collecting container is located.